Pretty much what the title says/$600 ea or all four for 2k.
I have four very neglected Acute2/D4 heads that are not even close to being compatible with my extension cables or my Pro B2r packs, so the only time they ever really got used was when I needed more than 5 heads (which resulted in pulling all the pro heads out, plugging the Acute2/D4 heads into the D4, and plugging the Pro heads into the B2r packs.
PITA.
So yes. They've just been sitting there.
